Dispositions - Land Dispositions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net gain (loss) on sales of land	$ 0	$ 11,825	$ 449
Disposal group, disposed of by sale [Member] | Plaza Yarrow Bay Properties [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net gain (loss) on sales of land		$ 11,800
Disposal group, disposed of by sale [Member] | Sorrento Mesa and Mission Valley Portfolio [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net gain (loss) on sales of land			$ 400